Doppler motion sensor apparatus and method of using same

ABSTRACT

An apparatus for, and method of, sensing characteristics of a vessel and a fluid conveyed therein.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application claims priority to and is a continuation-in-partof Israel Patent Application No. 185609 filed Aug. 30, 2007, titled“MULTI FUNCTION SENSSOR,” and International Patent Application No.PCT/IL2006/001416 filed Dec. 10, 2006, titled “IMPLANTABLE BIOSENSINGDEVICE AND HEALTH MONITORING SYSTEM AND METHOD INCLUDING SAME,” whichclaims the benefit of U.S. Provisional Patent Application Ser. No.60/748,218 filed Dec. 8, 2005, titled “WIRELESS INTEGRATED TRANSMITTERAND SENSOR,” the disclosures of which are expressly incorporated byreference herein.

The present application is related to U.S. Utility Patent ApplicationSerial No. (unknown) titled “OPTICAL SENSOR APPARATUS AND METHOD OFUSING SAME” filed on even date herewith, Attorney Docket No. CAT-P0001,U.S. Utility Patent Application Serial No. (unknown) titled “INTEGRATEDHEART MONITORING DEVICE AND METHOD OF USING SAME” filed on even dateherewith, Attorney Docket No. CAT-P0004, and U.S. Utility PatentApplication Serial No. (unknown) titled “METHOD AND SYSTEM FORMONITORING A HEALTH CONDITION” filed on even date herewith, AttorneyDocket No. CAT-P0005, the entire disclosure of each application beingexpressly incorporated by reference herein.

FIELD OF THE INVENTION

The present invention relates to sensing devices and, more specifically,to sensing devices for sensing the velocity of fluids.

BACKGROUND AND SUMMARY OF THE INVENTION

For medical reasons, in vivo parameters of a patient may need to bemonitored over a period of time. Heart arrhythmias are changes in thenormal sequence of electrical impulses that cause the heart to pumpblood through the body. Continuous monitoring may be required to detectarrhythmias because abnormal heart impulse changes might only occursporadically. With continuous monitoring, medical personnel cancharacterize cardiac conditions and establish a proper course oftreatment.

One prior art device that measures heart rate is the “Reveal” monitor byMedtronic (Minneapolis, Minn., USA). This device comprises animplantable heart monitor used, for example, in determining if syncope(fainting) in a patient is related to a heart rhythm problem. The Revealmonitor continuously monitors the rate and rhythm of the heart for up to14 months. After waking from a fainting episode, the patient places arecording device external to the skin over the implanted Reveal monitorand presses a button to transfer data from the monitor to the recordingdevice. The recording device is provided to a physician who analyzes theinformation stored therein to determine whether abnormal heart rhythmhas been recorded. The use of the recording device is neither automaticnor autonomic, and therefore requires either the patient to be consciousor another person's intervention to transfer the information from themonitor to the recording device.

Another known type of implantable monitoring device is atransponder-type device, in which a transponder is implanted in apatient and is subsequently accessed with a hand-held electromagneticreader in a non-invasive manner. An example of the latter type of deviceis described in U.S. Pat. No. 5,833,603.

A sensing device for acquiring signals and computing measurements isdisclosed herein. In one embodiment of the invention, the sensing deviceincludes a sensor having one or more transducers for transmitting andreceiving acoustic energy and converting the received acoustic energyinto one or more signals. The sensor is positioned facing a side of avessel. A computing device operates the sensor and processes theplurality of signals to obtain measurement values. The sensor and thecomputing device are enclosed in a housing.

A method for acquiring signals and computing measurements is alsodisclosed herein. One embodiment of the method comprises the steps ofproviding a sensing device as disclosed in the paragraph above,transmitting acoustic energy from the one or more transducers, receivingacoustic energy from the one or more transducers to obtain one or moresignals, processing the one or more signals to obtain measurementvalues, and analyzing the measurement values to obtain a parameter valueindicative of a characteristic of the fluid.

In another embodiment according to the invention, a device foracoustically measuring a characteristic of at least one of a bloodvessel and blood flowing through the blood vessel is provided. Thedevice includes a housing having a first side and a second side, asensor assembly, and a computing device. The sensor assembly is mountedto the housing and includes one or more transducers for transmittingacoustic energy through the first side of the housing, receivingacoustic energy though the first side of the housing, and converting theacoustic energy into signals. The computing device is configured toactivate the one or more transducers and interpret the signals todetermine the characteristic. The housing encloses the sensor and thecomputing device.

The features of this invention, and the manner of attaining them, willbecome more apparent and the invention itself will be better understoodby reference to the following description of embodiments of theinvention taken in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A is a schematic side view of a sensing device according to oneembodiment of the invention.

FIGS. 1B is an outwardly-facing view of the sensing device of FIG. 1.

FIGS. 1C is a perspective view of the sensing device of FIG. 1.

FIG. 2 and 3 are schematic side views of the sensing device of FIG. 1and a vessel.

FIG. 4 is a schematic top-side view of a Doppler sensor according to oneembodiment of the invention.

FIG. 5 is a conceptual vector representation of wave and fluid floworientations.

FIGS. 6A-6D are schematic front, side, top, and perspective views,respectively, of a Doppler sensor according to another embodiment of theinvention.

FIG. 7 is a schematic top view of a Doppler sensor according to anotherembodiment of the invention.

FIG. 8 is a conceptual view of a system adapted to transmit and receivecommunication signals from the sensing device of FIG. 1.

FIG. 9 is a flow-chart of a method according to the invention.

FIG. 10 is a schematic representation of a cardiac cycle.

Corresponding reference characters indicate corresponding partsthroughout the several views. Although the drawings representembodiments of the present invention, the drawings are not necessarilyto scale and certain features may be exaggerated in order to betterillustrate and explain the present invention. The exemplifications setout herein illustrate embodiments of the invention in several forms andsuch exemplification is not to be construed as limiting the scope of theinvention in any manner.

DETAILED DESCRIPTION OF EMBODIMENTS OF THE INVENTION

The embodiments discussed below are not intended to be exhaustive orlimit the invention to the precise forms disclosed in the followingdetailed description. Rather, the embodiments are chosen and describedso that others skilled in the art may utilize their teachings.

FIG. 1A illustrates a sensing device 1 according to one embodiment ofthe invention. Sensing device 1 generally includes a plurality ofcomponents including a Doppler sensor 60, a computing device 20, acommunication device 30, and an energy storage device 40, each of thecomponents mounted on a board 80 and being in electronic communicationwith computing device 20. The components are enclosed in a housing 90.In one embodiment, energy storage device 40 is adapted to receiveelectromagnetic energy waves 44 from an external energy source 46.

In one embodiment according to the invention, sensing device 1 isadapted to determine a physiological condition of a patient. By“patient” it is meant a person or animal whose physiological conditionis measured by sensing device 1. Although the invention disclosed hereinis described in the medical context, the teachings disclosed herein areequally applicable in other contexts where compact data acquisitionassemblies are desirable to perform measurements over time. For example,sensor assemblies according to the invention may be desirable insubmersed or difficult to reach applications, in dangerous environments,in applications having weight and size restrictions, in field researchactivities, and so on.

In one embodiment according to the invention, sensing device 1 isimplanted subcutaneously in the patient's body. It should be understood,however, that sensing device 1 may be implanted at different locationsusing various implantation techniques. For example, sensing device 1 maybe implanted within the chest cavity beneath the rib cage. Housing 90may be formed in the shape of a circular or oval disc, with dimensionsroughly the same as two stacked quarter dollar coins. Of course, housing90 may be configured in a variety of other shapes, depending upon theapplication. It may include four outwardly projecting loops 92, shown inFIGS. 1B and 1C, for receiving sutures in order to fix the assemblysubcutaneously within the patient's body. More or fewer loops 92 may beprovided depending upon the shape of housing 90. When so fixed, Dopplersensor 60 is positioned facing inwardly while an energy coupler, whichis described with particularity below, faces outwardly.

In another embodiment of a sensing device 1 according to the invention,Doppler sensor 60 and other features of the sensing device 1 areintegrated with an implanted cardiac device such as a pacemaker, aCardiac Resynchronization Therapy (CRT) device, an implantablecardioverter defibrillator (ICD), etc. In one embodiment, integrationmay be achieved by combining the components of the sensing device andthe cardiac device. If the cardiac device includes a computing device,for example, the algorithms that carry out the methods according to theinvention may be incorporated with the computing device of the cardiacdevice instead of adding a second computing device. In a similar manner,energy storage and communication devices may be combined to avoidduplication. In one embodiment, some components of the sensing deviceare included within the housing and some components are included withthe cardiac device. The cardiac device and the components in the housingare operably connected.

In another embodiment, sensing device 1 is positioned externally to thepatient's body. A support member is provided to support sensing device 1externally to the body. The support member may be permanently ortemporarily coupled to sensing device 1. In one embodiment, the supportmember comprises an adhesive layer for adhesively coupling the supportmember to the patient's body. In another embodiment, the support membercomprises a belt, which may be elastic, for holding sensing device 1against the patient's body.

Sensing device 1 may be implanted subcutaneously or positioned on thepatient with the aid of an external mapping system such as an ultrasoundmachine. Proper placement ensures that a vessel of interest is locatedwithin the sensing range of sensing device 1. Where the vessel ofinterest is the aorta, sensing device 1 may be positioned on the chestor back of the patient in a location that reduces interference by theribs of the measurements acquired in the manner described herein.

1. Doppler Sensor

A Doppler sensor comprises one or more transducers for insonating anobject and receiving reflected ultrasonic waves. The velocity of a fluidof interest may be determined by directing an insonifying wave ofultrasonic energy towards the fluid at a known angle, measuring thefrequency shift of the reflected ultrasound energy, and then calculatingthe velocity of the fluid. The Doppler frequency shift is proportionalto the component of the velocity vector that is parallel to theinsonifying wave. The velocity v of the fluid is determined by thefollowing equation:

v=f _(d) ·c/(2·f·cos θ)

where c is the velocity of sound in blood, f is the frequency of theinsonifying wave, θ is the angle between the wave and the velocityvector, and f_(d) is Doppler frequency shift.

A transducer is a device which converts acoustic energy into electricalsignals and vice-versa. Frequency shifts may be calculated by a varietyof methods depending on the method of operation of the transducer(s). Inone method of operation, the Doppler sensor may be a continuous wavesensor. A continuous wave Doppler sensor includes a transducer fortransmitting ultrasonic waves and a transducer for receiving ultrasonicwaves. The frequency shift in this method is measured directly bycomparing the two waves. In another method, a pulsed wave Doppler sensormay be used. A pulsed wave Doppler sensor has a single transducer fortransmitting and for receiving ultrasonic waves. After transmitting awave, the Doppler sensor switches from a transmitting to a receivingmode of operation. The frequency shift is measured by comparing phaseshifts between subsequently received waves. A plurality of wavestransmitted and received in sequence are necessary to calculate thephase shifts. Well known algorithms, such as the Kasai or thecross-correlation algorithms, may be used to obtain the phase shiftbetween the received and transmitted pulses.

Transducers may comprise coils, piezo-electric materials, and othersuitable transducers. Transducers may be focused so as to transmit anarrow wave, or beam, of acoustic energy. Transducers may also transmitbroad, or unfocused, waves of acoustic energy. Two or more transducersmay be combined in a linear array to transmit an acoustic wave capableof insonating a large area with a desirable amount of energy. By largeit is meant an area larger than what may be insonated with a singletransducer. Linear arrays may be connected such that they may be drivenas if they comprised a single transducer. Linear arrays may also beconnected such that each transducer segment operates as an independenttransducer.

FIG. 2 illustrates the relationship between a vessel 3 conveying blood 4having haemoglobin in red blood cells 5 and Doppler sensor 60 accordingto one embodiment of the invention. Doppler sensor 60 has transducer 61positioned facing towards a fluid 4 conveyed by vessel 3. A wave 62transmitted by transducer 61 is shown propagating along a directionindicated by centerline 63 which is perpendicular to the surface oftransducer 61. Arrow 6 indicates the direction of fluid 4 flow in vessel3. While Doppler sensor 60 is described herein to describe its functionin sensing assembly 1, other Doppler sensors described herein performthe same function and, in general, references to Doppler sensor 60 inthis and related patent applications are equally applicable to otherDoppler sensors described herein.

In one embodiment according to the invention, a driver device, e.g., apulse generator, provides an output corresponding to a desiredfrequency. The output may be amplified by an amplifier, such as atransistor, integrated with computing device 20 or provided externallyof computing device 20. The output may comprise a wave form. Computingdevice 20 may provide the frequency generation function. In analternative embodiment, a voltage is provided by the driver device tothe transducer corresponding to a desired ultrasonic frequency and thetransducer converts the electrical energy into acoustic energy in theform of an ultrasonic wave.

In one embodiment according to the invention, sensing device 1 has acommunication port for connecting to, and exchanging information with,other devices. Connector 85 is shown. The operation of connector 85,which is connected to other components of sensing device 1, is describedin more detail further below with reference to FIG. 8.

FIG. 3 illustrates a reflected ultrasonic wave 64. Wave 64 is shownpropagating along a direction indicated by centerline 63. Wave 64propagates in a direction opposite that of wave 62. Wave 64 also has afrequency that is different from the frequency of wave 62. Thedifference is determined by the selection of transducers. In oneembodiment, wave 62 is a continuous wave and wave 64 is reflectedcontemporaneously with wave 62. In another embodiment, wave 62 is apulsed wave transmitted by transducer A before reflected wave 64 reachestransducer A. Computing device 20 may direct transducer A to transmitwave 62 and measure the time required for wave 64 to reach transmitterA. The waves travel through soft tissue at a known constant velocity.The distance from transducer A along centerline 63 to vessel 3 may becalculated from the travel time between the transmission of wave 62 andreception of wave 64.

FIG. 4 illustrates Doppler sensor 70 including linear array transducersA, B and C according to one embodiment of the invention. Doppler sensor70 may be coupled or integrated with other components of sensing device1. Each of transducers A, B and C is operably connected with a driverdevice (not shown) that powers each transducer causing each transducerto transmit an ultrasonic wave capable of travelling a certain distanceto the fluid of interest and, upon reaching the fluid, reflecting aphase-shifted wave. Each of transducers A, B and C may be driven at adifferent frequency to distinguish the source of the reflected wavesreceived by Doppler sensor 70. For convenience, each transducer in alinear array is referred to herein as a transducer segment. In theembodiment shown, each linear array transducer comprises five transducersegments. Transducer segments may be operably connected to be activatedseparately or concurrently. Separate activation of one or moretransducer segments is desirable to limit power consumption. More thanone transducer segment may be activated concurrently to broaden thereach of the transmitted wave. Of course, if all segments in a lineararray are activated, the linear array operates as a single transducer.Doppler sensor 70 may comprise three such transducers.

Transducers A, B and C are disposed at an angle relative to each other.In one embodiment show in FIG. 4, transducers B and C are disposed at a45 degree angle relative to transducer A and at 90 degrees relative toeach other. Transducers may be positioned at different angles relativeto other transducers. The positions, and angles, are selected to orientacoustic energy in directions which optimally reflect acoustic energyfrom a vessel. Selection is based, at least in part, on the anatomy ofthe patient. The anatomy of the patient may determine where to positionsensing device 1, e.g., externally or implanted, positioned in front orback, and the position of sensing device 1 will determine the distancefrom a Doppler sensor to the vessel of interest. In one embodiment,transducers B and C are disposed at a 30 degree angle relative totransducer A and at 120 degrees relative to each other.

Transducer A includes segments A1 -A5, transducer B includes segmentsB1-B5, and transducer C includes segments C1-C5. Each segment maytransmit and receive ultrasonic energy in the form of waves. The arrowsoriginating at each segment and projecting perpendicularly to thesegment represent the direction of waves transmitted by each segment.Further, arrows 72, 74, and 76 represent the directions of wavesproduced by transducers A, B and C, in aggregate, respectively. Thefrequency of the acoustic energy is selected as a function of thedistance between the transducer and the target fluid. Transducers may beenergized, generally, at frequencies ranging between 2-10 MHz to reachblood conveying vessels at distances ranging, generally, between 3-20cm, after passing through the soft tissues of the patient. In oneembodiment, each of transducers A, B and C is energized at a frequencyranging between 2-10 MHz. In another embodiment, one or more segments oftransducer A are energized at a frequency of 5 MHz, one or more segmentsof transducer B are energized at a frequency of 4.5 MHz, and one or moresegments of transducer C are energized at a frequency of 5.5 MHz. Areflected wave may be measured at each segment of a linear arraytransducer. Each segment may be energized sequentially and may beenergized a plurality of times.

The Doppler shift, or frequency shift, is proportional to the componentof the velocity vector parallel to the impinging wave. Since the Dopplershift depends from the cosine of the angle θ between the wave and thevelocity vector, and the cosine function ranges between 0 and 1, signalsproduced by waves oriented parallel to the velocity vector produceoptimal signals. In one embodiment according to the invention, computingdevice 20 produces signals only from waves where the angle θ=θ₁ is lessthan or equal to 20 degrees. FIG. 5 shows conceptually the relationshipbetween velocity vector 6 and waves having directions 72, 74 and 76presented previously in FIG. 4. FIG. 5 also shows four arrows disposedat angle θ₁ relative to velocity vector 6. Arrow 74 is shown forming anangle with respect to velocity vector 6 which is smaller than θ₁.Consequently, waves oriented in the direction represented by arrow 74,in this case waves produced by linear array transducer B may generateusable signals. In contrast, waves oriented in the directionsrepresented by arrows 72 and 76, corresponding to transducers A and C,will not produce usable signals.

In one embodiment of the invention, sensing device 1 includes an opticalsensor assembly configured to detect the position and diameter of avessel. Sensing device 1 may determine, based upon the position of thevessel, which transducers will not produce usable signals and, to saveenergy, will only transmit ultrasonic waves from transducers that mayproduce usable signals.

To increase the range of the Dopper sensor, additional transducers maybe provided disposed different angles so that one or more of thetransducers may be positioned at angles which produce waves oriented atangles that are less than or equal to 20 degrees relative to thevelocity vector. In one embodiment, three transducers are arranged inthe shape of a K to enable Doppler sensor 70 to obtain a sufficientnumber of signals even when the relative position of Doppler sensor 70and vessel 3 change slightly with time or other factors such as apatient's activity level and posture. Reflected waves produced by onetransducer may be received by more than one transducer transducer.However, since waves have frequencies corresponding to each transmittingtransducer, Doppler sensor 70 is able to selectively filter signalsbased on the relative position of the corresponding transmittingtransducer and its transmission frequency so that the Doppler shifts maybe properly identified. The frequency shift corresponds to velocity aswell as to direction of flow.

In one embodiment, signals from waves received by segments of lineararray transducers A, B and C are filtered out when waves impinge onvessels other than the vessel of interest. The location of vessels otherthan the vessel of interest may be obtained in the same manner asrelative position data is obtained which will be explained below. Inanother embodiment, computing device 20 first determines the angle θ foreach segment and selectively energizes segments of transducers A, B andC only when the angle θ of a segment may generate usable signals,thereby saving energy. Furthermore, if all segments of a transducer mayproduce a usable signal, computing device 20 may limit the number ofsignals produced to save energy. For example, if all five segments arepositioned to produce a usable signal, computing device 20 may selectthree signals to conserve 40% of the energy necessary to generate fivesignals.

When multiple transducers comprising coils are positioned in closeproximity, each transducer may interfere with the operation of the othertransducers. Interference may be neutralized by an appropriate filteralgorithm. However, filtering in this manner requires additional memoryand energy to process the algorithm. FIGS. 6A-6D illustrate a Dopplersensor according to another embodiment of the invention. Doppler sensor170 includes transducers 171, 172 and 173 having coils 176, 177 and 178,respectively. FIGS. 6A, 6B, 6C and 6D are front, side, top, andperspective views, respectively, of Doppler sensor 171. Transducers 171,172 and 173 enclose coils 176, 177 and 178 on three sides designated bysymbol X with material configured to block electromagnetic waves, and ona fourth side designated by symbol Y with material configured to allowelectromagnetic waves to pass through. Side Y is referred to herein asan electromagnetic window. Blocking material may be any suitablematerial including a metal, and non-blocking material may be anysuitable material such as plastic. The blocking material physicallyeliminates interference between coils 176, 177 and 178 thereby savingenergy and enabling further miniaturization of sensing device 1 byreducing memory requirements. Transducers 171, 172 and 173 are stackedrather than being laid on a common plane. Computational requirements tocompensate for stacking, e.g., introducing a third-dimension to thegeometric distance calculations, consume negligible resources. In manycases, stacking effects may be ignored altogether due to theirnegligible effect.

FIG. 7 illustrates a Doppler sensor according to yet another embodimentof the invention. Doppler sensor 270 includes transducers 271-279 whichmay be single or linear array transducers. Transducers 271-279 arepositioned in the shape of three K's to provide a broader sensing reachwithout increasing the profile of sensing device 1 and, thus, withoutintroducing stacking variables to the calculations. More or fewertransducers may be used to suit the shape of the housing and thelocation where sensing device 1 is placed. In the embodiment shown,transducers 271, 274, and 277 comprise the base of the three K-shapedarrays. Transducers 271 and 277 are disposed at 30 degree angles withrespect to transducer 274, and each is disposed at 45 degree angles withrespect to the remaining two legs of each K-shape array.

As discussed previously, the calculation of blood velocity requiresknowledge of the incident angle θ between waves and vessel 3. Incidentangle and other data characterizing the relative position of vessel 3and a Doppler sensor may be obtained in various ways. Once obtained, itmay be stored in memory as reference values. In one embodiment, therelative position data may be provided to computing device 20 throughcommunication device 30 by an external device. The external device maytransmit wirelessly communication signals to communication device 30containing relative position data. In another embodiment, the relativeposition data may be provided to computing device 20 throughcommunication device 30 by another implanted device. Other implanteddevices include, without limitation, a pacemaker, a CardiacResynchronization Therapy (CRT) device, an implantable cardioverterdefibrillator (ICD), etc. In yet another embodiment, the relativeposition data may be provided to computing device 20 by another sensoror sensor assembly included in sensing device 1. A sensor assembly fordetecting the relative position of a vessel is provided in theabove-referenced related U.S. Utility Patent Application titled “OPTICALSENSOR APPARATUS AND METHOD OF USING SAME.” Once the selected signalshave been determined, computing device 20 computes a blood velocityvalue by comparing the frequency of transmitted and received wavesaccording to well known frequency-shift and angle algorithms or tables.

In another embodiment of a sensing device 1 according to the invention,a Doppler sensor and other features of the sensing device 1 areintegrated with an implanted cardiac device such as a pacemaker, aCardiac Resynchronization Therapy (CRT) device, an implantablecardioverter defibrillator (ICD), etc.

While sensing device 1 may be programmed to perform a measurement ofblood velocity relatively infrequently to conserve power (e.g., once ortwice per day), it should be understood that as battery technologyimproves, power conservation will be less of an issue, and measurementsmay be made more frequently. Moreover, when sensing device 1 is notimplanted (i.e., is worn by the patient externally), power may beprovided to sensing device 1 through connector 85, thereby eliminatingthe need to conserve power and permitting frequent or even continuousmeasurements.

2. Computing Device

Computing device 20 comprises a plurality of components. Whilecomponents are described herein as if they were independent components,the components may be combined in a single device such as an applicationspecific integrated circuit. Computing device 20 includes a processor, amemory, a program, inputs and outputs. The memory may include, but isnot limited to, RAM, ROM, EEPROM, flash memory or other memorytechnology. The processor and memory may be constructed in an integratedcircuit. The integrated circuit may include one or more of Dopplersensors 60, 70, 170 and 270, and communication device 30. Further,computing device 20 may include A/D and/or D/A converters on anintegrated circuit. Alternatively, A/D and/or D/A converters may beprovided separately.

The program represents computer instructions directing the processor toperform tasks responsive to data. The program resides in the memory.Data, including reference data and measurement data, also resides in thememory. Reference data may be stored in ROM or it may be stored in RAMso that it may be modified over time, either in response to externalinputs or in response to characteristics of measurement data collectedover time. Protocols for responding to measurement values may also beprovided. Protocols may be stored in permanent memory or may be storedin non-permanent memory such as RAM.

Computing device 20 controls the Doppler sensor 60, 70, 170, or 270 andcommunication device 30 through inputs and outputs. Computing device 20may control the number, frequency, power level and transmission of wavesby the Doppler sensor 60, 70, 170, or 270 to obtain the desiredmeasurements using the least amount of energy.

FIG. 8 discloses a system 300 for exchanging information with sensingdevice 1. System 300 includes sensing device 1 having, optionally,connector 85 (shown in FIG. 1A). System 300 may also include a computer302, a docking station 304 operably coupled to computer 302 via cable303, a telephone 306. In one embodiment of the invention, system 300transmits and receives communication signals wirelessly to/from sensingdevice 1 based on processing performed by computing device 20.

Connector 85 is adapted to plug into docking station 304. Sensing device1 is shown docked on docking station 304. While docked, sensing device 1may charge energy storage device 40. The docking station is operablycoupled to computer 302 to update the programs and reference valuesstored in the memory of computing device 20 prior to placing sensingdevice 1 on, or in, the patient. In another embodiment, sensing device 2is positioned externally to the patient and connector 85 isoperationally coupled to an energy source to power sensing device 2 andprevent depletion of energy storage device 40.

In a further embodiment according to the invention, additional sensorsand devices may be coupled to sensing device 1 through connector 85.Other sensors and devices may include, without limitation, additionalsensor assemblies 2, temperature sensors, pressure sensors, andaccelerometers. The other devices may or may not include a computingdevice. Other devices may also be incorporated with sensing device 1within housing 90. An integrated sensing device is disclosed in theabove-referenced related U.S. Utility Patent Application titled“INTEGRATED HEART MONITORING DEVICE AND METHOD OF USING SAME.” Theoperation of sensing device 1 may be adapted to operate the additionalsensors and devices by downloading into the memory of computing device20 modified programs adapted to operate them. Downloading may occurwhile computing device 20 is docked in the docking station.Alternatively, new programs may be downloaded wirelessly throughcomputing device 40.

FIG. 9 is a flowchart illustrating one routine of the program performedby computing device 20 according to one embodiment of the invention. Atstep 400, computing device 20 obtains transducer signals representativeof fluid velocity from a Doppler sensor. In one embodiment, transducersignals include voltage and frequency. It should be understood thatvelocity signals result from waves produced by a reflecting object. Inthe case of blood velocity, the objects are red blood cells. It isgenerally understood that the velocity of red blood cells in bloodaccurately represent blood velocity.

Step 400 may be initiated based on cardiac cycle data to define bloodvelocity at a particular point in the cardiac cycle. Step 400 may alsobe initiated in response to an external command received throughcommunication device 30 or as a result of detection of an abnormalcondition by sensing device 1. Each of transducers A, B and C areenergized sequentially. In one embodiment, transducer A transmits a waveand then switches to receive mode. Doppler sensor 70 detects thereflected waves in a manner determined by the configuration oftransducer A. Transducers B and C are activated in the same manner, insequence. In another embodiment, each transducer comprises atransmitting element and a receiving element and the transducer may,thus, be activated to simultaneously transmit and receive acousticenergy. The labelling of transducers or the energizing order areunimportant. More or fewer transducers may be utilized. The number andorientation of transducers are chosen to obtain data at angles relativeto vessel 3 which produce sufficient data for the intended purpose.

At step 402, computing device 20 processes the signals to obtainmeasurement values. Processing may involve removing inherent signalnoise, converting signals from analog to digital form, scaling,filtering out non-selected waves, and otherwise conditioning thedetected signals to convert them to measurement values. In oneembodiment, measurements obtained during one cardiac cycle are averagedto obtain an average blood velocity. In another embodiment, the high andlow value measurements obtained during one cardiac cycle are averaged toobtain an average blood velocity. An ECG may be used to estimate whenblood flows at a maximum or minimum velocity. After processing, measuredvalues may be stored in memory or may be analyzed to first determinewhether the values should be retained. Steps 400 and 402 may be repeatedas necessary to obtain sufficient measurement values to compute thedesired parameters in accordance with the teachings provided herein.

To save energy, it is desirable to operate Doppler sensor 70 only whenit is reasonably certain that a suitable signal will be obtained. In oneembodiment according to the invention, low-power consumption sensors maybe used to ascertain the angle of the vessel of interest relative toeach transducer before Doppler sensor 70 is activated. In oneembodiment, sensing device 1 includes an infrared sensor assembly 2,described with particularity in the above-referenced related U.S.Utility Patent Application titled “OPTICAL SENSOR APPARATUS AND METHODOF USING SAME.” Sensor assembly 2 ascertains that sensing device 1 ispositioned such that waves transmitted from transducers of the Dopplersensor intersect the velocity vector of blood at an angle approximatelyequal, or less than, 20 degrees. Transducers which are not positionedproperly are not energized.

At step 404, computing device 20 analyzes the measurement values.Analysis may include calculation of parameter data and/or diagnosisbased on measurement values. Parameter data refers to computed valuessuch as fluid velocity, cardiac output, cardiac rhythm, etc. Diagnosisrefers to the comparison of parameter values to reference values todetect an abnormal condition in the patient. Reference values are normalor expected values for the measured parameters for a particular patient.If an abnormal condition is detected, computing device 20 maycommunicate an alert rather than communicating measurement values asthey are collected (consuming unnecessary power) or waiting to transmitmeasurement values until the memory is full or a predeterminedtransmission time is reached (exposing the patient to unnecessary dangerduring the waiting period).

Steps 400, 402 and 404 may be performed concurrently. The apparatus andmethods of calculating velocity described above are useful incalculating the velocity of blood and other fluids. The velocitycalculations in the case of continuous fluid flow do not require furthercalculations. However, if fluid flow is cyclical rather than continuous,additional measurements and calculations are desirable to morecompletely characterize flow and to diagnose abnormal conditions basedon flow characteristics.

Blood velocity at a point in time depends on where that point in time isrelative to the cardiac cycle of the patient. The cardiac cycle has anelectrical component and a flow component. The electrical componentrefers to the electrical waves that cause the heart muscle to pump. Thewaves pass through the body and can be measured with a probe comprisingelectrodes that contact the body. An ECG is a good way to measurecardiac rhythms, particularly abnormal rhythms. An ECG is not, however,a reliable means for measuring the pumping ability of the heart.

FIG. 10 illustrates an ECG graph 500 of electrical activity of the heartshowing two cardiac cycles. A typical ECG consists of a P wave, a QRScomplex and a T wave. An isoelectric line 502 separates a T wave and thefollowing P wave. A PR interval 504 is measured from the beginning ofthe P wave to the beginning of the QRS complex. It is usually between120 and 200 msec long. A QRS complex is about 60 to 100 msec long. TheST segment connects the QRS complex and the T wave. A typical ST segmentlasts about 80 msec. In one embodiment, sensing device 1 includes an ECGsensor and an algorithm for detecting the T wave, the QRS complex andthe P wave.

Cardiac cycle may be obtained in various ways. In one embodiment,cardiac cycle may be provided to computing device 20 throughcommunication device 30 by an external device. The external device maytransmit wirelessly communication signals to communication device 30containing cardiac cycle data. In another embodiment, the cardiac cycledata may be provided to computing device 20 through communication device30 by another implanted device. Other implanted devices include, withoutlimitation, a pacemaker, a Cardiac Resynchronization Therapy (CRT)device, an implantable cardioverter defibrillator (ICD), etc.

In one embodiment, cardiac cycle data may be provided to computingdevice 20 by another sensor or sensor assembly included in sensingdevice 1. A sensor assembly for detecting the cardiac cycle is providedin the above-referenced related U.S. Utility Patent Application titled“OPTICAL SENSOR APPARATUS AND METHOD OF USING SAME.” In a furtherembodiment, cardiac cycle data may be provided to computing device 20 byan ECG sensor. A sensor assembly including an ECG sensor is provided inthe above-referenced related U.S. Utility Patent Application titled“INTEGRATED HEART MONITORING DEVICE AND METHOD OF USING SAME.”

In one embodiment according to the invention, steps 400, 402 and 404 arerepeated in groups comprising several measurements taken in shortsuccession to characterize systolic and diastolic blood pressure. Therepetitions provide blood velocity values at proximal points in timeduring a cardiac cycle. The groups of repetitions (e.g., five samples)may be timed based on cardiac cycle information to obtain blood velocitycorresponding to systolic and diastolic pressures. The systolic arterialpressure is defined as the peak pressure in the arteries, which occursnear the beginning of the cardiac cycle. The diastolic arterial pressureis the lowest pressure (at the resting phase of the cardiac cycle). Thetime of the systolic and diastolic pressures may be estimated to predictmaximum and minimum blood velocity.

As is further explained in the above-referenced related U.S. UtilityPatent Application titled “INTEGRATED HEART MONITORING DEVICE AND METHODOF USING SAME,” from velocity measurements obtained at a timecorresponding to systolic and diastolic pressures, and other informationsuch as vessel cross-section, sensing device 1 may compute systolic anddiastolic blood pressure. In one embodiment, sensing device 1 generatesfive velocity measurements at the time estimated to correspond tosystolic pressure and an additional five at the time estimated tocorrespond to diastolic pressure. Sensing device 1 may comparemeasurements within a group to determine a rate of change consistent orinconsistent with the expected change in blood velocity. Upon detectingunexpected changes indicating an abnormality, sensing device 1 mayperform a function as described below.

Reference values may include target values and acceptable variationranges or limits. Reference values may also include values ofmeasurements obtained from other sensors or from other devices throughcommunication device 30 including, without limitation, relative positionvalues.

Parameter values may indicate an abnormality when they fall outsidereference target values or ranges. In some embodiments, parameter valuesmay produce a statistic such as, for example, a moving average, and anabnormality would be detected when the parametric statistic differs froma reference statistic by more than an expected amount. If parameter datadiffers from expected values by more than a predetermined amount,computing device 20 may initiate a new measurement cycle to verify theparametric data before diagnosing an abnormality.

One abnormal medical condition is cardiac arrhythmia. Computing device20 may be configured to perform an analysis of the measurement values todetermine, for example, whether the cardiac rhythm is irregularindicating arrhythmia.

Additional abnormal medical conditions may be detected using valuesobtained externally or from additional sensors. Additional sensors whichmay be included in sensing device 1 are disclosed in theabove-referenced related U.S. Utility Patent Applications titled“OPTICAL SENSOR APPARATUS AND METHOD OF USING SAME,” “INTEGRATED HEARTMONITORING DEVICE AND METHOD OF USING SAME” and “METHOD AND SYSTEM FORMONITORING A HEALTH CONDITION.”

At step 406, computing device 20 transmits an alert if an abnormalcondition is detected, particularly a condition determined to be aserious or dangerous condition according to a prescribed protocol. Thealert may be used to actuate an alarm or to alert the patient to takeremedial action. A remedial action may be terminating or reducingphysical activity. The alert may also provide global positioning (GPS)information to an emergency service. Referring to FIG. 6, the abnormalcondition, when found to be present, may also be displayed on a computer36 and/or transmitted via communication device 30 to a caregiver. Thealert may comprise a text message or a code corresponding to thecondition. Computing device 20 may also initiate a new measurement cycleand measure on a continuous basis in response to the detection of anabnormal condition.

At step 408, computing device 20 may initiate a treatment. Sensingdevice 1 may receive, through communication device 30, an externalcommand to perform a treatment in response to the alert. Optionally,based on the protocol, an abnormal condition may also be used to directa device adapted to provide treatment to deliver such treatment.Treatment may include, for example, an electric shock or a drugdelivery.

At step 410, the parameter values or other information are communicatedto an external device. Step 410 may be performed concurrently with anyof the above steps. The parameter values may be stored in memory andtransmitted wirelessly by communication device 30. The communicationsignal from communication device 30 may be activated on a periodicbasis, in response to an abnormal condition, in response to anexternally received command, whenever memory usage exceeds apredetermined amount, or whenever the energy storage level is determinedto be low, the latter two conditions established to prevent data loss asa result of memory overflow or energy loss. It should also be understoodthat sensing device 1 may include communication devices in addition tocommunication device 30. For example, where communication device 30 is acellular modem, sensing device 1 may also include a backup Bluetooth orRF communication device. Such a backup device may be desirable insituations where, after a number of attempts, it becomes apparent thatthe cellular modem is unable to transmit information (e.g., due to lowavailable power, poor network coverage, etc.). In such a situation,computing device 20 may activate the backup communication device totransmit information or an alert to an alternate external receivingdevice.

Step 410 may be performed, for example, once an abnormal condition hasbeen detected so as to update a caregiver on a substantially real-timebasis. Step 410 may also be performed at regular intervals, such as oncea day, once a week, once a month, etc. Alternatively or in addition tothese transmissions, computing device 20 may be programmed to respond torequests for data received by communication device 30 (e.g., from ahealth care provider) by causing communication device 30 to transmit therequested data or information representing the requested data.

The communication signal may be received by equipment near the patientto alert the patient to the condition, or received remotely (such asover a network) by a healthcare provider, relative, or otherpredetermined recipient.

3. Communication Device

Referring again to FIG. 8, a system 300 adapted for transmitting andreceiving a communication signal according to one embodiment of theinvention is illustrated therein. Communication device 30 is a two-waycommunication device, e.g. via the cellular telephone system and/or theGPS satellite system. Communication device 30 includes an antenna fortransmitting and receiving communication signals. The communicationsignals travel wirelessly to and from one of a plurality of optionalexternal communication devices.

An external communication device may be a computer 302 or any electronicdevice capable of wirelessly receiving a communication signal, such astelephone 306 which is exemplified as a cellular phone. Telephone 306may also be an emergency service switchboard or a hospital or medicalcenter switchboard. By communication signal is meant a signal that hasone or more of its characteristics set or changed to encode informationin the signal. By way of example, and not limitation, communicationsignals include acoustic, RF, infrared, other wireless media, andcombinations of any of the above. An external communication device mayalso be a relay unit located externally of the patient's body, e.g.clipped to the patient's belt. The relay unit may include a receiver forreceiving the transmissions from communication device 30, and atransmitter for re-transmitting the communication signal to anotherexternal communication device. The relay unit may also be stationary andhardwired for connection to the internet or direct connection to ahealthcare provider's computer. Likewise, the relay unit may receive acommunication signal from a healthcare provider and transmit the signalto communication device 30.

The communication signal from communication device 30 may include avoice message, a text message, and/or measured data. The communicationreceived by communication device 30 may include data, such as updatedreference data, or commands. A command may include, for example,instructions to computing device 20 for performing a task such asproviding a treatment to the patient, collecting and transmittingadditional data, or updating the reference data.

4. Energy Storage Device

Referring again to FIGS. 1A, 1B and 1C, a system for recharging energystorage device 40 may be provided in one embodiment according to theinvention. Computing device 20 receives energy from energy storagedevice 40. Energy storage device 40 includes an energy storage componentsuch as a battery. Optionally, sensing device 1 may also include anenergy coupler for receiving energy from an external source to chargeenergy storage device 40.

One example of an energy coupler is an electromagnetic device, such asinduction coils 42, for receiving external electromagnetic signals 44and converting such signals into electrical energy for recharging theenergy storage component. An external electromagnetic device 46generates electromagnetic signal 44 which is received and converted intoelectrical energy by energy storage device 40. Energy storage device 40may provide a charge signal to computing device 20. Computing device 20may compare the charge signal to a reference charge signal and initiatea low charge communication signal for alerting the patient and/orhealthcare providers. Alternatively, a detector, such as a voltagesensor, may be used to monitor the charge of energy storage device 40and provide a signal to computing device 20 when the charge falls belowa threshold. Electromagnetic device 46 may be placed near sensing device1 to charge energy storage device 40.

Energy may instead, or additionally, be provided in the form ofultrasonic vibrations. For example, a piezoelectric transducer may beincluded in sensing device 1. An ultrasonic vibration may be providedexternally. The transducer generates electricity when driven byultrasonic vibrations.

While this invention has been described as having an exemplary design,the present invention may be further modified within the spirit andscope of this disclosure. This application is therefore intended tocover any variations, uses, or adaptations of the invention using itsgeneral principles. Further, this application is intended to cover suchdepartures from the present disclosure as come within known or customarypractice in the art to which this invention pertains.

1. A sensing device for acquiring signals and computing measurementscomprising: a sensor including one or more transducers for transmittingacoustic energy, receiving acoustic energy, and converting the receivedacoustic energy into one or more signals, the one or more transducersfacing a side of a vessel; a computing device operating the one or moretransducers and processing the one or more signals to obtain measurementvalues; and a housing enclosing the sensor and the computing device. 2.The sensing device of claim 1, wherein the computing device includes analgorithm for computing a parameter value of a fluid conveyed by avessel.
 3. The sensing device of claim 2, wherein the parameter is fluidvelocity.
 4. The sensing device of claim 3, wherein the fluid is bloodand the parameter value is blood velocity.
 5. The sensing device ofclaim 1, further including a communication device for transmitting andreceiving a communication signal.
 6. The sensing device of claim 5,wherein the communication signal includes a relative position valuerepresenting the position of the vessel.
 7. The sensing device of claim5, wherein the communication signal includes an alarm.
 8. The sensingdevice of claim 5, wherein the communication device includes a connectoradapted to operably couple to one or more of a docking station, a secondsensing device, and an energy source.
 9. The sensing device of claim 1,wherein the housing is configured for subcutaneous implantation.
 10. Thesensing device of claim 1, wherein the sensing device is integrated withan implanted cardiac device. 11 .The sensing device of claim 1, whereineach of the one or more transducers comprises a linear array oftransducer segments.
 12. The sensing device of claim 11, wherein thetransducer segments are selectively activated to transmit and to receiveacoustic energy.
 13. The sensing device of claim 12, wherein eachtransducer segment may be selectively operated to transmit acousticenergy and to receive acoustic energy.
 14. The sensing device of claim1, wherein at least one of the one or more transducers transmitsacoustic energy at a different frequency than the frequency of theacoustic energy transmitted by another of the one or more transducers.15. The sensing device of claim 1, wherein the one or more transducersare positioned at an angle relative to each other.
 16. The sensingdevice of claim 1, wherein the sensing device is dimensioned about thesame as two stacked quarter dollar coins.
 17. The sensing device ofclaim 1, further including an energy storage device.
 18. The sensingdevice of claim 17, wherein the energy storage device includes an energycoupler for receiving energy to recharge the energy storage device. 19.The sensing device of claim 1, wherein each transducer includes a sourceof acoustic energy, the transducer having a window for allowing passageof acoustic energy, and the source of acoustic energy being partiallysurrounded by material for blocking passage of acoustic energy andpreventing interference between adjacent transducers.
 20. A method foracquiring signals and transmitting data comprising: providing a sensingdevice including one or more transducers for transmitting acousticenergy, receiving acoustic energy, and converting acoustic energy intoone or more signals, the one or more transducers facing a side of avessel, a computing device for operating the one or more transducers andprocessing the one or more signals to obtain measurement values, and ahousing enclosing the sensor and the computing device; transmittingacoustic energy from the one or more transducers; receiving acousticenergy from the one or more transducers to obtain one or more signals;processing the one or more signals to obtain measurement values;analyzing the measurement values to obtain a parameter value indicativeof a characteristic of the fluid.
 21. The method of claim 20, whereinthe fluid is blood and the parameter is blood velocity.
 22. The methodof claim 21, wherein the fluid is blood and the parameter is bloodpressure.
 23. The method of claim 22, wherein the blood pressureparameter includes systolic pressure and diastolic pressure.
 24. Themethod of claim 20, further including the step of obtaining relativeposition values and storing the relative position values in memory. 25.The method of claim 24, wherein the obtaining step includes receivingrelative position values from the communication device and storing therelative position values in memory.
 26. The method of claim 24, whereinthe sensing device includes an optical sensor, wherein the obtainingstep includes receiving relative position information from the opticalsensor and converting the relative position information into relativeposition values.
 27. The method of claim 20, further including the stepsof diagnosing a condition using the parameter value and performing afunction in response to the diagnosing step.
 28. The method of claim 27,wherein the condition is an abnormal condition.
 29. The method of claim28, wherein the function is communicating an alarm.
 30. The method ofclaim 28, wherein the function is initiating a treatment.
 31. The methodof claim 30, wherein the treatment is an electric shock.
 32. The methodof claim 30, wherein the treatment is delivering a drug.
 33. The methodof claim 28, wherein the function is communicating data with thecommunication device on a continuous basis.
 34. The method of claim 26,wherein the condition is a normal condition and the function iscommunicating information on a periodic basis.
 35. The method of claim20, wherein the receiving step includes sequentially obtaining signalsfrom at least some of the one or more transducers to compute a parametervalue.
 36. The method of claim 20, wherein each of the one or moretransducers comprises a linear array of transducer segments.
 37. Themethod of claim 36, further including the step of selecting one or moretransducer segments and preventing transmission and reception ofacoustic energy by unselected transducer segments.
 38. The method ofclaim 36, wherein the selecting step includes determinig an incidenceangle of acoustic energy relative to the direction of fluid flow andchoosing transducer segments when the incidence angle is smaller than,or equal to, 20 degrees.
 39. The method of claim 37, wherein the sensingdevice further includes the optical sensor, and the selecting stepincludes identifying with the optical sensor any transducer segmentwhere the acoustic energy transmitted by the transducer segment isobstructed and choosing unobstructed transducer segments.
 40. A devicefor acoustically measuring a characteristic of at least one of a bloodvessel and blood flowing through the blood vessel, the device including:a housing having a first side and a second side; a sensor assemblymounted to the housing and including one or more transducers fortransmitting acoustic energy through the first side of the housing,receiving acoustic energy though the first side of the housing, andconverting the acoustic energy into signals; a computing deviceconfigured to activate the one or more transducers and interpret thesignals to determine the characteristic.
 41. The device of claim 40,wherein the characteristic is a velocity of the blood.
 42. The device ofclaim 40, wherein the one or more transducers are positioned at an anglerelative to one another.
 43. The device of claim 40, wherein thecomputing device individually activates each of the one or moretransducers sequentially to determine the velocity of the blood.
 44. Thedevice of claim 40, wherein the sensor assembly comprises acousticenergy blocking material and includes windows for transmitting andreceiving acoustic energy.
 45. The device of claim 40, wherein thehousing is made of acoustic energy blocking material and includeswindows for transmitting and receiving acoustic energy.